Do you realize that they will keep attacking as soon the funeral ends right?
do you think that is a good idea while all the troll tribes are there and unite the entire troll empire against the alliance?
Anduin also avoids killing civilians to not prove sylvana's point, right now the horde is probably going to face another rebelion, all what the alliance needs to do is wait until they start killing each other.
If anduin attacks during the funeral, that rebellion probably wouldn't be as successful.
jaina also literally said that she would never become like arthas or garrosh.
and the alliance also had to recover as well.
Anduin then says that they will keep pushing towards victory. he is not stopping.